Apparatus for electrolysis of fused alkali chlorids.



UNTTED sTATEs PATENT o-EErcE.

EWALD STEINBUCH, OF MONTHEY, SWITZERLAND, ASSIGNOB TO SOCIETY OF CHEMI- CAL INDUSTRY IN .BASLE, OF-BASEL, SWITZERLAND.

APPARATUS FOR ELECTROLYSIS OF FUSEID ALKALI CHLORIDS.

Specification of Letters Patent.

Patented Oct. "F, 11913.

Application filed August 23, 1910. Serial No. 578,554.

To all whom it may concern Be it known that I, EWALD STEINBUOH, a citizen of the Swiss Republic, and resident of Monthey. Canton of Valais, Switzerland, have invented certain'new and useful Improvements in Apparatus for Electrolysis of Fused Alkali Chloride, of which the following is a full, clear, and exact specification.

The construction of a practicable apparatus, for obtaining economically alkali metal and chlorin by the electrolysis of fused chlorids is a problem which has not hitherto been satisfactorily solved. It is essential that the alkali metal which is separated at the cathode should .be withdrawn from the sphere of action of the chlorin simultaneously liberated at the anode, in order that a favorable yield per unit of current may be achieved. Moreover the apparatus mustbe of a size suitable for use in a factory and the separate parts of it must have a degree of resistance which will assure a reasonable life and therefore the'desired economical working. An attempt to combine in an apparatus these several requirements has met with numerous chemical, physical and constructional difiiculties. In

the first place it is difficult to find a material which resists the action of alkali metal and chlorin in equal degree, so that the use of simple separating walls or diaphragms between the cathode and anode compartments leads to only a poor result. For this reason it has been necessary to use double diaphragms adapted on the cathode side to withstand the attack of the alkali metal and on the anode side that of the chlorin. There is, however, a further defect, namely that the materials which become into question are either from the first conductors of electricity or become conductors owing to the comparatively high temperatures necessary for the electrolysis of the molten mass. Thus it happens that in the usual arrangement of diaphragms these either, after some time, become short-circuited with the oathode by the alkali metal and themselves act as cathodes, or being in the path of the lines of current they become a part of the circuit as bi-polar electrodes and are thus quickly destroyed so that the desired result, namely an apparatus of long life, is not attained.

Attempts in another direction, namely to separate the cathode and anode compartments by cooled, and, if necessary, hollow diaphragms closed at their lower part upon which an insulating layer of solid salt may form, have not led to the construction of an apparatus in which an economical produc tion of alkali metal and chlorin is possible; the like may be said of the attempt to use two vessels communicating with each other and made of materials adapted to resist chlorin and alkali metal respectively. Finally most of the apparatus hitherto proposed suffer from the defect that the fusion of the salt or mixture of salts must be effected by application of heat from without so that the vessel is generally quickly destroyed by the action of the heating gases.

The present invention relates to an apparatus designed to overcome all aforesaid difficulties in the electrolysis of fused alkali c-hlorids.

According to the invention the apparatus is such that on the one hand the alkali metal floating on the melted salt remains insulated from the cathodes and on the other hand the spaces for the collection of the products of th electrolysis are separated by at least two diaphragms which are not attacked by the fused electrolyte. These diaphragms on the cathode side are of material adapted to withstand alkali metal and on the anode side of a material adapted to withstand chlorin, and their physical constitution is such that they are permeable to the lines of current without discharge of ions or they are so arranged that they are not in the principal path of the current lines.

In the accompanying drawings are shown several constructions of apparatus according to the invention, the several figures being diagrammatic and vertical sections through the electrolytic bath.

Figures 1 and 2 are sections of the same cell in planes at right angles to each other while Figs. 3 and 4: are sections of two other cells.

lis a furnace of rectangular cross section built of fireproofbrick and constitutes the electrolytic cell. The metal cathode 2 is introduced into the'cell from below through a sleeve 4 in which the current lead 3 is packed with magnesite or the like. The anodes 5 are suspended from a suitable cover which closes the chlorin chamber ing the alkali metal.

tightly. The diaphragms 6, made of material adapted to withstand chlorin, are built into the walls of the cell. They may extend from the cover into the cell only so far that they dip a few centimeters below the surface of the melted salt, or farther than this. In the latter case they are perforated at the parts which extend beneath the surface of the melted salt so that they do not prevent passage of the current lines. These diaphragms provide a closed chamber for the chlorin rising from the anodes and from thi chamber the chlorin escapes through suitable ducts 7 in the brickwork. The alkali metal separated at the cathode,

- on account of its low specific gravity tends to rise to the surface of the melted salt. Since, however, owing to the upwardly moving bubbles of chlorin in the electrolyte there is a rapid mechanical current in the direction from the cathode to the anodes, the larger part of the alkali metal libcr ated at the cathode would be carried toward the anodes where it will again combine with the chlorin. In order to prevent this there are provided between the diaphragms 6 and the cathode 2 further diaphragms 8 which are perforated or made of wire netting or of louver-formed sheets; these are duly insulated from the cathode. Between them the" alkali metal rises to the surface of the melted salt into a bell 9 extending over the diaphragms 8; from this bell the metal flows to the pipe 13. Instead of using a separate hell 9 the diaphragms 8 may be extended upward to form walls without perforations so as to constitute the chamber for collect- It has been found advantageous to provide between the diaphragms 8 and the cathode 2 a further duly separated wire net or the like 1.0. The number of these nets between 8 and 2 may be increased to any suitable extent. In-

stead of introducing the cathode 2 from below it may be inserted from above between the diaphragms 8. Care must be however, that it is fully insulated at the part where it passes through the layer of alkali metal and down to the point where the perforations of the diaphragms 8 begin. When the cathode is introduced from below, as shown in Figs. 1 and 2, the insulation of the conductor by the sleeve 1 is not absolutely necessary; it is always advisable, however, in order to prevent direct contact with the cathode of the mud which always settles on the bottom of the cell during protracted working. Further parts of the apparatus shown in Figs. -1 and 2 are the metal helices 11 which are brought into circuit for the purposes of startingthe melting of the electrolyte, and the transverse rods 12 which serve as electrodes for completing the fusion of the electrolyte. These parts 11 and 12 may be combined together taken,

in any suitable manner. Also the cathode can serve the function of one of the electrodes 12.

The apparatus works as follows: The metal resistances 11. are'connected with any suitable source of alternating current and brought to alow red heat. The salt or mixture of salts to be electrolyzed is gradually introduced and melted until the melted mass comes into cont-act with the electrodes 12. The alternating current is new switched on to the electrodes 12 between which it passes through the molten salt the resistances 11 which may have the form of bands instead of helices either remain in the cell or are withdrawn). While this heating by means of alternating current between the electrodes 12 is continued further quantities of salt are introduced until the cell is full to the desired height, that 'is to say until the level of the molten mass is within a few centimeters of the pipe 13. The cover with the anodes 5 is then put on tightly and after the alternating current has been cut off the cathode 2 is connected with the negative pole of a source of continuous current and the anodes 5 with the positive pole thereof. Ghlorin is liberated at the anodes and escapes through the ducts 7. The alkali metal liberated at the cathode 2 collects to a depth of a few centimeters as a layer 14: on the surface of the melted salt and flows away into any suitable receptacle through the.

pipe 13. The salt to be electrolyzed, such as common salt, is charged into the anodecompartment or into the space between the diaphragms (Sand 8. The dimensions of the apparatus and the current densities at the electrodes and in the electrolyte are so proportioned that no injuriously high temperature can be produced. If for any reason the electrolysis is interrupted the continuous current is cut off and alternating current again passed through the molten mass by means of the electrodes 12 so as to maintain the electrolyte liquid.

It will be seen that the layer of alkali metal floating on the electrolyte does not come to conducting contact with the cathode so that a short-circuit between the'cathode and the said metal or ratus serving to collect the alkali metal does not occur. The separation of the alkali metal at places where this is not desirable is thus avoided. Furthermore, owing to the use of two-fold diaphragms made of material adapted to resist alkali metal and chlorin respectively, these parts are not corroded by the products of electrolysis. Finally these diaphragms when they are such a position in the cell that they stand in the path of the current through the electrolyte are so constructed that the lines of current pass unhindered, that isto say without discharge of ions, (8 and 10, Fig. 1) or they the parts of the appaacreage are arranged in such a position in the. cell that they do not extend into the path of the lines of current; (6, Fig.1) thus by one or other of these arrangements it is avoided that the diaphragms become a part of the circuit as bi-polar electrodes, i

' Various modifications may be madein the apparatus; for instance instead of a cell of rectangular section as shown in Figs. 1 and shown in Fig. 4 the electrodesare super-' imposed, the anode '5 being below the oath ode 2. In order that the chlorin'contained in the anode may not enter the cathode compartment the'space between the diaphragms (3 is closed below by anasbestos or like sheet 10 adapted to resist c'hlorinso that the gas evolved is directed sidewise. As before 6 represents the diaphragms adapted to resistchlorin and- 8 -those adapted to resist alkali metal. 3 is the conductor forthecathode, 4 an insulating sleeve which prevents contact of the alkali metal 14 with the cathode or its conductor. In similar; mannerthe anode can be the upper electrode and the cathode the lower, in which case the sheet 10 may be a fine meshed wire netting which will deflect laterally the alkali metal rising from the cathode.

What claim is:

1. In an apparatus forobtainingmolten' alkali metal and chlorin by the electrolysis of. a molten mass containing alkali chlorid, the combination of an anode and of a oath ode with two I horizontallyjuxtaposed chambers for collecting separately the products of the electrolysis and with partitions separatingas'well'the said chambers as the saida iodeand cathode, which are all e p'a-' ble offlre'sisting attack by the electrrliiyte, are made of metal at their. parts co" ing into contact with the molten alkali- [metal and of a mineral substance at their parts coming into contact-with chlorin,---in order that they can also resist attackby the-products of eleotrolysiscoming into contact with them and are providedjwith interstices-filled with molten electrolyteat their parts which serve to prevent a recombination of the said products of electrolysis'and are in the/field of the main current, so" that at these parts they-are permeable to the ll'nes of current without discharge of ions, while the remaining massiveparts of the said partitions are so arranged relatively to the anode and the cathode that they are substantially not subjected to the action of the electric cur-- rent, the specified parts of the apparatus being arranged in such a manner that the molten alkali metal collected in one of the said chambers remain insulated from the cathodic parts.

2. In an apparatus alkali metal and chlorin by the electrolysis of a molten mass containing alkali chlorid, the combination of an anode and of a cathode with two horizontally juxtaposed chambers for collecting separately-the products of the electrolysisand with substantially vertical partitions separating as well the said chambers as the said anode and cathode which are capable of resisting attack by the electrolyte, are made of metal at their parts coming into contact with molten alkali metal and of a mineral substance at their parts coming into contact with chlorin, in order that-they can also resist attack by the products of electrolysis coming into con tact with them and are provided with interstices filled with molten electrolyte at their parts which serve to prevent a recombination of the said products of electrolysis and are in the field of the main current, so that at these parts they are permeable to the lines of current without discharge of ions, while the remaining massive parts of the said partitions are so arranged relatively to the stantially not. subjected to the action of the electric current, the specified parts of the apparatus being arranged in such a manner that the molten alkali metal collected inone of the said chambers remains insulated from the cathodic parts. 4

3. In an apparatus for obtaining molten alkali metal and chlorin by the electrolysis of a molten mass containing alkali chlorid, the combination of an anode and of a cathode with two horizontally juxtaposed chambers for collecting separately the products of the electrolysis, with heating resistances and additional electrodes for melting the electrolyte by alternating current and with partitions separating as well the said chambers as the anode and the cathode, which trolyte, are

and of a mineral substance at their parts coming into contact with chlorin, in order that they can also resist attack by the products of electrolysis coming into contact for' obtaining molten v anode and the cathode that they are subv arecapable of resisting attack by the elecade of metal at their parts coming into contact with molten alkali metal with them and are provided with interstices filled with molten electrolyte at their parts .which serve to prevent a-recombination of the said products at. electrolysis and are in the held of the mam current, so that at these parts they are permeable to the lines of current withoutdischarge of ions, while its the remaining massive parts of the said partitions are so arranged relatively to the anode and the cathode that they are substantially not subjected to the action of the electric current, the specified parts of the apparatus being arranged in such a manner that the molten alkali metal collected in one of the said chambers remains insulated from the cathodic parts.

" 4. In an apparatus for obtaining molten alkali metal and chlorin by the electrolysis of a molten mass containing alkali chlorid. the combination of an anode and of a cathode with two horizontally juxtaposed chambers for collecting the products of the electrolysis. with heating resistances and addi-' tional electrodes for melting the electrolyte by alternating current and with Substantially vertical partitions separating as well the said chambers as the cathode and anode, which are capable of resisting attack by the electrolyte, are made of metal at their parts coming into contact with molten alkali metal and of a mineral substance at their parts coming into contact with chlorin, in

order that they can also resist attack by the products of electrolysis coming into contact with them and are provided with interstices filled with molten electrolyte. at their parts which. serve to prevent a recombination of the said products of electrolysis and are in the field of the main current, so that at these parts they are permeable to the lines of current without discharge of ions, while the remaining massive parts of the said partitions are so arranged relatively to the anode and thecathode that they are substantially not subjected to the action of the electric current, the specified parts of the apparatus being arranged in such a manner that the molten alkali metal-collected in one of the said chambers remains insulated from the cathodic parts.

In witness whereof I have hereunto signed my name this sixth day of August 1910, in

the presence of two subscribing witnesses. EVVALD STEINBUCH.

Witnesses:

Y. E. MAYER,

C. STETTLER. 

